Fatal error: unexpected found nil while unwrapping an optional values - ios

Question

whole code is like this:
var inputStream :NSInputStream?
var outputStream:NSOutputStream?
NSStream.getStreamsToHostWithName(ip, port: port, inputStream: &inputStream, outputStream: &outputStream)
let reader = inputStream
let writer = outputStream
writer?.open()
reader?.open()
var message : UInt8 = 0
while reader!.read(&message, maxLength: 1)>0
{
let wa = NSString(bytes: &message, length: 1, encoding: CFStringConvertEncodingToNSStringEncoding(CFStringEncoding(CFStringEncodings.GB_18030_2000.rawValue))) as! String
}
when the message i receive is a chinese character, the last line throws this:
fatal error:unexpected found nil while unwrapping an optional value, at the mean time, the value of message is 196
does anybody know how to solve this problem?

Answer 1

According to this page, if the byte you read is in the range 0x81-0xfe, the character is encoded using two or four bytes, so trying to decode just the first byte will fail. The NSString constructor will return nil, and attempting to unwrap it (with as! String) will throw that error.
You need to check what byte you read, and read another byte if necessary based on the first byte. Then you need to check the second byte, and possible read two more bytes. Finally, you need to pass all of the one, two, or four bytes to the NSString constructor in a single buffer.

Answer 2

Try to change message type for inputData like this for example:
let queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
dispatch_async(queue) {
let bufferSize = 1024
var message = Array<UInt8>(count:bufferSize, repeatedValue: 0)
while true {
let bytesRead = self.inputStream!.read(&message, maxLength: bufferSize)
let responseString = NSString(bytes: message, length: message.count, encoding: NSUTF8StringEncoding) as! String
// Do somthing with response
...
}
}